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BIOL 1090
Peter Dawson

9/25/2012 9:28:00 AM What type of protein is represented by: A. Peripheral Membrane Protein B. Peripheral Membrane Protein C. Integral Membrane Protein 2. Would you expect the following regions to be hydrophobic or hydrophilic? Why? D. Hydrophobic (highly) interacts with fatty acyl chains E. Hydrophilic (highly) interacts with aqueous ECM 3. What is a polarized cell? Spatial organization of organelles A cell containing distinct plasma membrane domains (i.e, apical, lateral, basal) Composed of distinct proteins giving rise to distinct properties (i.e directional transport of molecules or adhesion) 4. Is a nerve cell a polarized cell? Explain. Yes different regions of the plasma membrane contain distinct proteins. Some regions (Dendrites) contain proteins involved in receiving incoming signals. Other regions (terminal knobs) contain proteins involved in transmitting signals to target cells. Other regions (axon) conduct impulses away from the cell body. 5. Define active transport. Transport of a substance against its gradient The process by which a substance binds to a transmembrane protein to allow the movement of a substance against its electrochemical gradient using energy. The Dopamine Transporter The dopamine transporter is responsible for the reuptake of dopamine from the synapse. It clears the dopamine from the synapse by pumping it back into the neuron (using active transport) Dopamine transporter is an integral membrane protein with 12 Transmembrane domains - The Dopamine is moved into the cell against its concentration gradient thus energy is required to move it across Reuptake of dopamine by the dopamine transporter is active transport The DAT is a contransporter -couples active transport to an existing ion gradient . The Na/K-ATPase establishes a gradient of Na ions -the concentration of NA is higher outside the cell than inside the cell the Na gradient is stored energy -The gradient is needed to transport the dopamine The DAT uses this energy to move 2NA ions down its gradient and 1 dopamine molecule against its gradient it also moves 1 Cl ion into the cell Since the NA and dopamine are moving in the same direction (into the cell) this is called symport. 3 Sodiums get in the door, it turns the sodium gets kicked out the other side and at the same time 2 potassiums get in . Phosphate that is released from the ATP is bound to an amino acid and the potassium kicks off the phosphate from the amino acid and it causes a change in the pump. Ultimately you end up with a lot of sodium on the outside and a lot less potassium on the inside even though you have a different charge you have a much different charge on the outside than on the inside so the job of the pump is to create an electrochemical gradient that can be used to power the symport of the DAT Dopamine and the Pump High Sodium on the outside, Low sodium within and Dopamine are outside and 2 sodiums go in and bring in a dopamine with them. This occurs across the synapse. Carries the dopamine with them through the dopamine transporter into the dopaminergic neuron using an electrochemical gradient formed by the Na/K ATPase Drugs and DAT Some drugs act by competing for the DAT -Amphetamine, Meth, Ecstasy, mephedrone, resemble structure of dopamine and use the DAT To enter the cell -They compete with dopamine therefore less dopamine enters the cell -once inside the cell they also reverse the action of the DAT -The DAT moves dopamine into the synapse -blocks transporter therefore NO REUPTAKE OF DOPAMINE FROM THE SYNAPSE -The Dopamine transporter is perisynaptic (located beside the synapse). If plasma membrane are fluid and dynamic how is this specific localization maintained. ________ Where is DAT synthesized? -It is synthesized at the Rough endoplasmic reticulum by membrane bound riboso
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